Reducing EEG Artifacts during a Home Study
Take these steps to decrease the amount of EEG artifacts while recording in any home you visit
The beauty of an EEG study done in the home is that you can capture a patient in their natural environment. They will experience stimuli that they experience on a daily basis. Their brain may react differently to sunlight shining in through a window or off a large screen TV near their bed, for example. It’s true that EEG studies done in the home can provide alternative insights as to what may cause seizures compared to those done in an epilepsy monitoring unit (EMU) or clinical environment.
The risk, however, is that artifacts can appear on the study and obstruct the data that EEG technologists, physicians, and researchers so eagerly want to see. After all, the home is not a sterile environment. Let's take a quick look at what artifacts are and how EEG artifacts occur.
Artifacts: A Refresher
One of the advantages of recording EEG signals is that movement of the patient can be allowed. The disadvantage lies where these signals can become polluted with noise in your collected data. Thankfully, the impact of artifacts can be decreased significantly. Trained technologists can spot common occurrences such as eye blinking with relative ease.
Artifacts are commonly placed in two categories: Physiological (coming from the patient) and Non-physiological (coming from the environment around the patient). Some examples of physiological artifacts are eye movements, muscle movements (EMG), sweat from the patient, swallowing, ECG (heart signals), and breathing. Essentially anything the patient does impulsively will be considered physiological. Examples of non-physiological artifacts include low-frequency electromagnetic fields like those from AC power lines and other electronics, wire movement from the electrodes, and electrode pops. Much of this article will focus on non-physiological artifact reduction because studies done in the home will have a more challenging environment for capturing clean data.
Take the following steps prior to starting the study to ensure that artifacts are reduced as much as possible. EEG artifact removal isn't likely, but you want to create an EEG recording that is as clean as possible. Use the techniques to help!
1. Check your impedances
Good connections are perhaps the most important way you can reduce artifacts on a recording. You want to have balanced impedances, which means that the impedances of the electrodes are approximately the same on all of the connections. Remember that common-mode rejection theory states that high or imbalanced impedances will increase the noise level and provide a poorer signal.
Be sure to look at your ground and reference impedance. These electrodes are vital and are key to making sure your impedances are balanced. Poor grounding can cause a significant impact.
2. Establish electronic isolation whenever possible
Reduce the risk of artifacts by isolating electronic components. If you need to plug a system into a home outlet, try to have it be the only electronic using the outlet. Other electronic signals can interfere with the quality of your recording, so wrap the electrode lengths with tape fully to minimize stray wires from picking up those signals.
Using a notch filter may help remove artifacts in the high frequency 60 Hz or 50Hz range, (relatively high compared to the lower frequency of many brain waves) but comes with the understanding that slight distortions of the data can occur.
While Bluetooth is an excellent way to capture data, you don’t want a house full of Bluetooth signals jamming up your recording quality. Ask patients or caregivers to turn off all unnecessary Bluetooth devices during a study, so that a study doesn’t have to happen more times than it’s needed. Remember that a lot of devices use Bluetooth these days: television remotes, ear pods, cell phones, game controllers, laptops, computer mice, and speakers.
3. Manage your equipment carefully
When you cannot control your environment as well as you would be able to in a clinic or hospital setting, you have to settle for what you can control: your equipment. After all, you have a job to do.
To get the most out of a study, make sure your equipment is placed properly. Instruct the patient or caregiver to keep EEG recorders away from other electrical appliances when possible. Microwaves, TVs, gaming consoles, computers, and even phone chargers (the opposite side of a charger, too) can create artifacts. Keep electrical cords away from EEG system cords and electrodes while preventing them from overlapping. Use common sense and don’t let patients place their phone under their pillows when they sleep.
4. Beware of interference from unexpected places
You’re probably aware of electronic interference coming from the usual suspects. Are you frequently checking if interference isn’t coming from other sources?
Water can not only cause interference, but it can be a safety risk, depending on the equipment. Showering or bathing during a study is prohibited. The patient also shouldn’t be fidgeting with their amplifier, head wrap, or electrodes in any way. When they think they aren’t being monitored they might create artifacts - even by accident. This goes back to the importance of having a quality EEG headwrap as you begin the study. The less swaying the wires do, the more comfortable the patient will be and your study quality will not be compromised by noise. It can make such a big difference!
Pets can cause interference when they are being petted on a patient’s lap. Invisible fence collars or other electronic transmitting devices pets might be wearing could be an unexpected problem as they wander from room to room. Don’t let Fido be the culprit behind the unnecessary artifacts in your waveforms. Basically, if it’s an electronic device or can conduct electricity, consider the effect it could have on your EEG study.
For the good of the patient and an accurate EEG recording, try to be proactive in reducing artifacts by following these standard procedures before the study begins.
This educational information is brought to you by Lifelines Neuro.